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separate- the last three (propyl, butyl, and amyl). The poly-
h yd ric alcohols,glycol,glycerol, and mannitol, and also substances
like the sugars are extremely soluble, for the proportion of OH
groups to rarbon is high. Ordinary phenol requires for solution
i 5 parts of water, whereas the di- and tri-hydric phenols readily
dissolve. The same applies to acids. The lower monobasic
aliphatic acids (formic, acetic, propionic, and normal butyric)
are easily soluble in water, whereas /.wbutyric requires 3 parts
and valeric about 30 parts of water. The last three separate
from watrr on the addition of salt. The dibasic and hydroxy-
ac'uls, ^'herr the proportion of carbon is small (succinic, tartaric,
and citric-, are naturally more soluble than the monobasic
arids having ihc same number of carbon atoms.
The majority of aromatic acids are not very soluble in water
at thr ordinary temperature, for the proportion of carbon to
carboxy! is high ; the hydroxy- and polybasic and also amino-
acids arc more soluble than the unsubstituted monobasic acids
; or, if substituted, where thr substituents are halogens or nitro-
-..M'oups, which diminish, as a rule, the solubility). One thousand
parts of water dissolve about 2l> parts of ben/.oic, 2\ parts of
-uilicylic, tS parts of phlhalic, and 159 parts of mandelic acid.
A< ids Mich as gallic and tannic acids are readily soluble in water.
Thr sulphonir acids and also many of their salts are very
Thr lowrr aliphatic amines and amides are soluble in water,
but not thr higher members, nor the simple aromatic amines ;
but some diainines, ammo-phenols and ami no-acids are moder-
ately soluble. Many of these soluble compounds may be
extracted with ether after salting-out (adding common salt to
.saturation). If the substance is soluble in water," it maybe one
of thr abo\e-named compounds, or a lower aldehyde or kelone,
or a bisulphite compound of these substances, or the salt of a
base or acid.
Tin- following is a list of the more soluble organic compounds
their boiling-points, melting-points and solubilities, which are
roughly indicated by the letters .v. (soluble in cold water) 7/..9.
f'Uaublr in hot water;.